The 3:30 a.m. blaze that destroyed the Islamic Society of Joplin's mosque was the second suspicious fire at the facility in a month, The Joplin Globe reported. A July 4 fire damaged the mosque's roof.
The fire also came the day after a gunman opened fire at a Sikh temple in Wisconsin, killing six people and wounding three before he was killed by police.
Michael Kaste, special agent in charge of the FBI office in Kansas City, said about 30 agents were assigned to the mosque fire, which he said would be characterized as "suspicious" until a cause is determined.
"If this fire is determined to be deliberate in nature, it will be investigated to the fullest extent possible," Kaste told the Globe. "Any act of violence to a house of worship is taken very seriously by law enforcement, and threatens the very core of the safety and security that our communities enjoy."
A $15,000 reward is being offered in the July 4 fire and would be extended to Monday's fire if it is ruled an arson.
Imam Lahmuddin, the mosque's religious leader, said members would find another location to hold prayer services or will pray at home.
"We just take this as a test from God. God is testing us," he said. "This is the month of Ramadan. We are fasting. We are not supposed to get angry. We are not supposed to say anything bad. But that's not only for this month, but for every day of our lives."
Carl Junction Fire Chief Bill Dunn also said the fire was suspicious, but authorities had yet to conclude it was arson.
U.S. Sen. Roy Blunt, R-Mo., issued a statement by e-mail, saying he was "incredibly saddened" to hear about the fire.
"If it turns out to be arson once again, this kind of action is absolutely unacceptable," he said.